Virginia's Declaration of Rights was drawn upon by Thomas Jefferson for the opening paragraphs of the Declaration of Independence. It was widely copied by the other colonies and became the basis of the Bill of Rights.
The ridges found in flexible metal duct create turbulence and will diminish airflow. NEVER use 4 dryer duct or any plastic duct on a range hood installation. The minimum size duct allowed on most range hoods is 3 Â¼ by 10 which is equivalent to 6 round. More powerful hoods require even larger duct sizes up to 10 round. Consult the specifications for the model you have chosen.
Those microwave range hoods are ideal over an electric or an induction cooktop, as you can get away with an 18-20 clearance. (a microwave installed so the bottom of it sits 30 above the cooktop is only good if you happen to be 6'6 or taller!).